AIR TRAVEL -- once a luxury, now mass transit -- long ago outgrew the facilities it uses across this country. Airports must be expanded and improved dramatically -- which means with big bucks that haven't been there to spend lately. The money and the results could both materialize with new certainty, however, under a measure passed by the House on Thursday, which would allow a new head tax on airline passengers and provide for other financing improvements. The legislation would permit local airports to charge up to $12 per round trip for improved services -- a user fee that is a key component of the Bush administration's transportation program. Practically and politically, it makes sense.

The tax proposal is part of a bill that would authorize significant spending from the Airport and Airways Trust Fund, which is financed by an existing 8 percent federal tax on airline tickets as well as by taxes on aviation fuel. The trust fund has had a surplus of $7.6 billion, which many members of Congress have argued should have been spent instead of squirreled. The bill would let most of this surplus be spent during the next five years for projects that would include modernization of the national air traffic control system.

Opponents of the new head tax have complained that it would come on top of President Bush's 1991 budget request seeking an increase in the existing federal ticket tax to 10 percent. That proposal is among the tax options being considered by the White House and congressional budget negotiators now seeking ways to cut the deficit. But transportation experts in and out of the administration say that both the federal tax and the airport head tax will be needed to make the necessary improvements to the country's airport system.

During the past 15 years, airports have not been built to keep pace with passenger traffic. Between 1978 and last year, for example, the number of airline passengers increased from 266 million to 480 million. Officials expect that in another 10 years the number could hit 750 million.

Despite the victory in the House, support in the Senate remains a question. But as advocates argued in the House debate, federal funding alone won't meet the needs for airport improvements at the same time that the government must spend for its new national air system. These latest agreements on financing could unlock federal funds while letting airports raise still more. It's a sound response to long neglected air travel needs at a time of efforts to reduce the federal deficit. Senate approval would let this proceed as it should: soon.